Re: OT: why no file copy() libc/syscall ??

[jw schultz]

On Tue, Nov 11, 2003 at 10:51:10AM +0100, Ihar 'Philips' Filipau wrote:
> Florian Weimer wrote:
> >Andreas Dilger wrote:
> >
> >
> >>>This is fast turning into a creeping horror of aggregation.  I defy 
> >>>anybody
> >>>to create an API to cover all the options mentioned so far and *not* 
> >>>have it
> >>>look like the process_clone horror we so roundly derided a few weeks ago.
> >>
> >>	int sys_copy(int fd_src, int fd_dst)
> >
> >
> >Doesn't work.  You have to set the security attributes while you open
> >fd_dst.
> 
>   int new_fd = sys_copy( int src_fd );  /* cloned copy, out of any fs */
>   fchmod( new_fd, XXX_WHAT_EVER );      /* do the job. */
>   ...
>   flink(new_fd, "/some/path/some/file/name"); /* commit to fs */

The associate open file descriptor with a new path system
call (flink here) has already been rejected for solid
security reasons.

>   close(new_fd);  /* bye-bye */
> 
>   I beleive this can be more useful. Not only in naive tries to replace 
> cp(1) with kernel ;-)

Eliminating the flink and using file descriptors you wind up
with something like:

	in_fd = open(oldpath, O_RDONLY);
	fstat(in_fd, statbuf);
	out_fd = open(newpath, O_WRONLY|flags, statbuf->st_mode);
	sendfile(out_fd, in_fd, 0, statbuf->st_size);
	close(out_fd);
	close(in_fd);

So if you can do it with open file descriptors why do you
need a new system call?

-- 
________________________________________________________________
	J.W. Schultz            Pegasystems Technologies
	email address:		jw@xxxxxxxxxx

		Remember Cernan and Schmitt
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